The gripes about Disneyland crowds started on opening day - July 17, 1955 - when so many people showed up that refreshment stands ran out of food and drinks.

Sixty years later, Disneyland is celebrating its diamond anniversary with a new pulsating nighttime parade and upgraded fireworks show plus a sparkling veneer on Sleeping Beauty's castle. Theme park experts predict that visitors will pack the park to near capacity, based on the 8.5 percent increase in attendance - to 14.5 million visitors - for the 50th anniversary.

Disneyland managers say they have been testing several crowd management tactics to make sure that the throngs attending the celebration, which begins Friday, don't bottleneck like the freeway traffic around the Anaheim, Calif., park.

"We've been doing things over the past couple of years to prepare for this," said Mary Niven, vice president of Disneyland Park.

The tactics include opening "bypasses" - little-used routes behind and parallel to Disneyland's Main Street to help move people in and out of the park. Crews will also direct foot traffic in a one-way, counterclockwise direction around the night parade to reduce gridlock. The park also plans to employ staff to entertain guests waiting in line.

Disneyland officials won't discuss daily attendance numbers, but theme park experts estimate that the 85-acre park draws an average of about 44,000 people a day.

For a few hours last Christmas morning, Disneyland reached capacity - a ceiling that has never been publicly disclosed but some insiders have said is 80,000 visitors. The gates were closed, and would-be parkgoers were encouraged to visit neighboring Disney California Adventure Park.

Walt Disney Co. Chief Executive Robert Iger recently confirmed that plans are in the works to expand Disneyland. He has yet to offer details.

"Physically there is not a lot they can do with the site," said Dennis Speigel, president of International Theme Park, a consulting firm in Cincinnati. "They only have so much space."

Making the most of the park space is crucial to Disney's bottom line. The company's parks and resorts unit posted operating income of $566 million for the three months that ended March 28, a gain of 24 percent from a year earlier. The company said the strong performance was partly due to increased guest spending and attendance at its domestic properties.

Over the years, Disney executives have employed several strategies to contend with the throngs.

Disneyland introduced a virtual queuing system known as FastPass in 1999 to manage lines.

Excessive crowding prompted Disney executives last year to temporarily halt sales of popular annual passes for Southern California residents. The park also adopted a new policy for disabled guests in 2013 because visitors were hiring people in wheelchairs to bypass the long ride lines.

Keeping crowds happy

With heavy crowds expected during the 60th anniversary, Disneyland managers say they have an arsenal of tactics to cut down on guest frustration over bottlenecks and queues.

On the Jungle Cruise ride, an employee dressed as a boat skipper will joke with waiting visitors. Children in line for the Toy Story Midway Mania ride can play with Etch-A-Sketch toys.

During the parades along Disneyland's Main Street, park employees will encourage guests to use the sidewalks as one-way streets, traveling in a counterclockwise direction to keep foot traffic moving smoothly around the parade. It's a tactic that the park relied on heavily during its 50th anniversary celebration.

If Disneyland reaches capacity, the park will temporarily close its gates and direct visitors to California Adventure. This takes place only a few times a year, primarily during the holiday season, park managers say.

The biggest crowding problems are likely to hit at night when crowds gather along Main Street to see the newly upgraded "Paint the Night" parade, followed by the overhauled fireworks show.

To disperse the crowds and reduce congestion, the park has scheduled the parade to start at nearly the same time as "Fantasmic," the musical pyrotechnic show at Rivers of America in Frontierland. The tactic forces guests to choose between the attractions.

At Disney California Adventure, the water and light show known as "World of Color" begins each night at about the same time as the Disneyland parade.

"The timing of the shows was something we worked on to minimize the impact on guest congestion," Vice President Kris Theiler said.

When Main Street becomes too congested, Disneyland has the option of opening two alleyways behind the shops to quickly move crowds.